PdZn　alloy　has　been　shown　to　catalyze　methanol　steam　reforming　(MSR),　producing　hydrogen　gas　and　carbon　dioxide　with　high　selectivity.　Despite　many　studies,　the　mechanism　for　MSR　on　this　catalyst　is　still　not　completely　understood.　In　this　work,　several　possible　pathways　of　MSR　are　explored　using　a　plane-wave　density　functional　theory.　The　focus　is　placed　on　the　reaction　network　starting　from　a　facile　reaction　between　adsorbed　formaldehyde　and　hydroxyl　species,　produced　from　the　decomposition　of　methanol　and　water,　respectively.　These　pathways　were　found　to　have　barriers　lower　than　the　rate-limiting　step,　namely,　the　dehydrogenation　of　methoxyl,　and　they　involve　species　that　have　been　detected　in　various　experiments.　Interestingly,　the　reaction　pathways　share　many　similarities　with　the　MSR　process　on　copper,　which　is　the　traditional　catalyst　for　MSR.　©　2011　American　Chemical　Society.